Über die Bildung von Dihydro-1,2-oxazin-N-oxiden durch intramolekulare Addition eines Nitronat-Anions an eine Carbonylgruppe

The Formation of Dihydro-1,2-oxazine N-Oxides through an Intramolecular Addition of a Nitronate Anion to a Carbonyl Group Highly substituted 4-keto-1-nitroalkanes cyclize under basic conditions to dihydro-1,2-oxazine N-oxides. These N-oxides are thermally unstable and decompose to 1,4-diketones, BF₃ catalyzes a similar decomposition, but probably via a different mechanism.     

Generalized fractional programming: Algorithms and numerical experimentation

Several algorithms to solve the generalized fractional program are summarized and compared numerically in the linear case. These algorithms are iterative procedures requiring the solution of a linear programming problem at each iteration in the linear case. The most efficient algorithm is obtained by marrying the Newton approach within the Dinkelbach approach for fractional programming.     

A remark on two-dimensional stokes flow solutions

Summary It is shown that the solution of Laplace's equation is useful to obtain a unique Stokes stream function which is valid everywhere under limited circumstances. When the Stokes stream function fails at infinity the use of the Oseen solution is required to obtain a physically acceptable solution.

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Résumé Les solutions de l'équation de Laplace permettent d'obtenir des fonctions de courant au sens de Stokes uniques et valides en tous points de l'espace, dans certains cas seulement. Quand les fonctions de courant au sens de Stokes ne sont pas valides à l'infini l'utilisation de functions de courant au sens d'Oseen est nécessaire pour obtenir une solution physiquement valable.

     

Mixed effect of the supporting electrolyte and the zinc anode in the electrochemical homocoupling of 2-bromopyridines catalyzed by nickel complexes in an undivided cell

[reactions: see text] Nickel-catalyzed electroreductive homocoupling of 2-bromomethylpyridines and 2-bromopyridine has been investigated in an undivided cell in the presence of a zinc sacrificial anode. A series of reactions were performed with various types and concentrations of supporting electrolyte. It was observed that a key step in this process is the formation of an arylzinc through a nickel-zinc transmetalation. This intermediate can be transformed back to the reactive arylnickel species to afford the homocoupling as the final product. The back process from the arylzinc intermediate is, however, suppressed in the presence of high concentration (0.2 M) of tetraalkylammonium salts. On the contrary, with NaI, the formation of the dimer is not prevented, whatever the NaI concentration.     

Hydrogen-bond accepting strength of protonated nicotine

Recent crystal structures of nicotine bound to the acetylcholine binding protein (AChBP) ended a long debate confirming that the pyridine nitrogen of nicotine is indeed hydrogen-bonded to receptor residues through a bridging water molecule. Here, we describe the first direct experimental evaluation of the hydrogen-bond affinity of the nicotinium pyridine nitrogen. The equilibrium constant of its association with a phenol is 1 order of magnitude greater than the association of the acetylcholine carbonyl oxygen.     

Sur les semi-caracteres des groupes de Lie resolubles connexes

Let G be a connected solvable Lie group, π a normal factor representation of G and ψ a nonzero trace on the factor generated by G. We denote by $\text{D}$(G) the space of C^∞ functions on G which are compactly supported. We show that there exists an element u of the enveloping algebra U$\text{G}$_$\text{c}$ of the complexification of the Lie algebra of G for which the linear form $\text{? ψ(π(u 1 ?))}$ on $\text{D}$(G) is a nonzero semiinvariant distribution on G. The proof uses results about characters for connected solvable Lie groups and results about the space of primitive ideals of the enveloping algebra U$\text{G}$_$\text{c}$.     

Monitoring the formation of TTF dimers by Na+ complexation

The formation of the two dimeric species [(TTF)2]+* and (TTF+*)2 can be monitored by complexation of Na+ on a calix[4]arene-TTF assembly.